Ultrasound systems employing ultrasonic transducers are widely used in medical applications to visualize muscles and internal organs, as well as during pregnancies to view the fetus in the womb. While many different types of transducers are used, a typical transducer includes a transducer element which sends out high-frequency sound waves to be reflected off body structures. The transducer element is often attached to a motor which allows the transducer element to rotate, swing and/or vibrate within the transducer. The motor is encased within the housing of the transducer while the transducer element is located within a membrane outside of the housing, the motor and the transducer element being connected by a rotating shaft. An ultrasound coupling fluid is placed inside the membrane in contact with the transducer.
During an ultrasound examination, a liquid gel or coupling fluid is often applied on the patient over the area to be scanned. The coupling fluid is placed within the transducer membrane surrounding the transducer element. After the gel is applied, the membrane of the transducer is placed on and moved over the area being examined by a sonographer. Meanwhile, the transducer element is being mechanically rotated within the membrane of the transducer throughout the examination.
While the fluid may be necessary to ultrasound transmission, the motor can become damaged if it comes into contact with the fluid. Accordingly, the transducer housing is often designed to separate the fluid in the membrane from the motor. Nevertheless, the fluid often leaks into the housing and contacts the motor through the opening in the housing for the rotating shaft. Accordingly, what is needed is a seal that fits around the rotating shaft that prevents the fluid from reaching the motor. The seal must be small enough to fit inside the transducer, it must allow for rotation of the shaft, and it must be flexible enough to account for the natural vibrations of the rotating shaft during use, all the while preserving the integrity of the seal.
With respect to the prior art, mechanical arrangements for incorporating seals around a rotating shafts are commonly used, and such seals are used in medical devices, such as ultrasound transducers. For example, U.S. Pat. No. 4,655,462 discloses a coil spring seal which can be used around a rotating shaft to prevent leakage.